The decomposition of water into hydrogen and oxygen is considered an ideal way to store energy. While this decomposition can be accomplished by the electrolysis of water, that process is not as efficient as alternative, more complicated processes. One very efficient process for decomposing water is a hybrid electrolytic-thermochemical process which consists of two reactions: EQU 2H.sub.2 O+SO.sub.2 .fwdarw.H.sub.2 +H.sub.2 SO.sub.4 ( 1)
and EQU 2H.sub.2 SO.sub.4 .revreaction.2H.sub.2 O+2SO.sub.2 +O.sub.2 ( 2)
Since sulfuric acid is the product of sulfur trioxide plus water, the second reaction can be represented as: EQU 2SO.sub.3 .revreaction.2SO.sub.2 +O.sub.2
The first reaction is accomplished electrochemically and the second reaction takes place in a thermal reduction reactor.
In the second reaction the oxygen produced is recovered and the sulfur dioxide and unreacted sulfur trioxide are recycled. The achievement of a maximum possible conversion of SO.sub.2 per pass through the thermal reduction reactor is required for good heat economy and reasonably low recycle mass rates. Experiments have shown, however, that the purely thermal conversion of SO.sub.3 to SO.sub.2 is slow and has a poor yield.
To overcome this poor yield, various catalysts have been used. The one that is economically acceptable and has been shown to sufficiently accelerate the rate of conversion of SO.sub.3 to SO.sub.2 is commercially available alumina (Al.sub.2 O.sub.3) supported alpha hematite (.alpha.-Fe.sub.2 O.sub.3). However, erosion of the hematite from the surface of the alumina support material takes place in the commercial catalyst due to poor adherence of the hematite to the alumina. This physical degradation of the catalyst results in decreasing catalytic activity as a function of time. As a result, the amount of SO.sub.2 produced decreases accordingly. Should the eroded hematite be transported sufficiently far downstream of the reaction zone, where the equilibrium of reaction 2SO.sub.3 .revreaction.2SO.sub.2 +O.sub.2 shifts to the left, SO.sub.2 can be oxidized back to SO.sub.3. Additionally, the lines of the decomposition reactor become clogged. But with the exception of this difficulty, an .alpha.-hematite alumina supported catalyst works very well in this reaction.